For example, a liquid crystal display device comprises a liquid crystal display element (i.e., a liquid crystal display part, a liquid crystal display panel, an LCD or a liquid crystal display panel) in which two insulating substrates (hereinafter referred to as electrode substrates) made of transparent glass are superimposed on each other with a predetermined space therebetween in such a way that their surfaces on which display transparent pixel electrodes, an alignment film and so forth are formed are opposed to each other, both substrates are bonded to each other with a sealing material which is provided in a frame-like shape in a marginal portion between both substrates, a liquid crystal which is hermetically enclosed inside the sealing material between both substrates, the liquid crystal being charged inside the sealing material through a liquid crystal charging port provided in part of the sealing material, and polarizers are provided on the outside of the respective substrates; a backlight disposed below the liquid crystal display element and arranged to supply light to the liquid crystal display element; a driving circuit board for driving the liquid crystal display element, which is disposed outside the marginal portion of the liquid crystal display element; a frame-shaped body which is a molding for holding the above members; a metallic frame in which all the members are housed and a liquid crystal display window is formed; and other associated members.
The liquid crystal display element and the driving circuit board are electrically connected by, for example, a tape carrier package (hereinafter referred to as the TCP) equipped with a semiconductor integrated circuit chip for driving the liquid crystal display element. More specifically, a multiplicity of output terminals of the circuit board and a multiplicity of input terminals (input outer leads) of the TCP are connected by soldering, and a multiplicity of output terminals (output outer leads) of the TCP and a multiplicity of input terminals of the liquid crystal display element which are connected to the respective display electrodes are connected by means of an anisotropic conductive film (such input terminals are formed in an array at an end portion of a surface of one of the transparent glass substrates which constitute the liquid crystal display element, i.e., a surface of one of the electrode substrates). A multiplicity of input terminals of the semiconductor integrated circuit chip provided on the TCP are connected to a multiplicity of output inner leads of the TCP, while a multiplicity of output terminals of the semiconductor integrated circuit chip are connected to a multiplicity of inner leads of the TCP.
Such a liquid crystal display device is described in documents such as Japanese Patent Laid-Open No. 214E48/1986 and Japanese Utility Model Laid-Open No. 137E5/1990.
FIG. 24 is a schematic plan view showing essential portions of part of the wiring formed on an electrode substrate which constitutes a conventional liquid crystal display element, i.e., display electrodes, terminals for connection to electrodes of a TCP, and lead-out wiring for connecting both.
Display electrodes 46 which are made of transparent conductive film and are wired in parallel and constitute pixels are formed on a surface of an electrode substrate (311 or 312) which includes one of insulation substrates which are made of transparent glass and constitute a liquid crystal display element (no shown in FIG. 24. See reference numeral 18 of FIG. 13). Reference numerals 41 denote terminals (connecting electrodes) connected to the terminals (the output outer leads) of a TCP which is a driver element (not shown in FIG. 24. See reference numeral 74 or 77 of FIG. 13). Reference numerals 45 denote oblique straight wiring which are lead-out wiring which connects the display electrodes 46 and the terminals 41, respectively. Reference numeral 40 denotes the center line of a terminal group which corresponds to a single TCP mounted on the electrode substrate 311 or 312, and reference numeral 44 denotes a portion in which a sealing material is provided.
Conventionally, in the electrode substrate (311 or 312) which constitutes the liquid crystal display element, the array pitch of the electrodes of the TCP, i.e., the pitch of the terminals 41 connected to the terminals of the TCP is made narrower than the array pitch of the display electrodes 46 wired in parallel. Accordingly, the lead-out wiring which connect the display electrodes 46 and the terminals 41 are formed as the oblique straight wiring 45. As shown in FIG. 24, in the case of the conventional lead-out wiring, both the angle of each conductor of the oblique straight wiring 45 (to the corresponding display electrode 46 or terminal 41) and the width of each conductor of the oblique straight wiring 45 are adjusted so that the wiring resistances of the respective conductors of the lead-out wiring become equal. Such a pattern of lead-out wiring is called radial wiring.
Such prior art has the following problems.
One problem is that the area use efficiency (wiring efficiency) of the lead-out wiring on the electrode substrate 312 is low, their lengths are large and their wiring resistances are large. If the lead-out wiring are intended to be shortened, the width of each conductor of the lead-out wiring must be made narrow so as to provide a clearance (space) between each conductor of the lead-out wiring, so that the problem of an increase in wiring resistance occurs. Presently, the wiring resistances of lead-out wiring are, for example, 500 .OMEGA. to 1 k.OMEGA., and are large compared to 500-700 .OMEGA. which are the output resistances of driving semiconductor IC chips.
In addition, there is a vacant space between each group of the terminals 41 connected to the terminals (electrodes) of a plurality of TCPs which are installed in a line on an end portion of an electrode substrate, and since the terminals are made of, for example, ITO (indium-tin-oxide; Nesa) film, a difference in height between the area in which the terminals are present and the area in which the terminals are absent is produced by the film thickness of the terminals. The ITO film is as thick as 0.2-0.5 .mu.m. This leads to the problem that during mass-production of liquid crystal display elements, such uneven shape is transferred to a rubbing roller for subjecting alignment treatment (rubbing) to an alignment film formed on the display electrodes, and if such rubbing roller is used to perform alignment treatment, uneven rubbing grooves are formed in the alignment film and the display quality is lowered.
Furthermore, since the oblique straight conductors 45 of the lead-out wiring are radially wired, the spaces between the conductors of the oblique straight wiring 45 becomes nonuniformly narrower from the display electrodes 46 toward the terminals 41 as shown in FIG. 24. This leads to the problem that nonuniform shading occurs in a portion which originally needs to be uniformly black, within a so-called frame portion which is a non-lighting portion outside the display portion (a lighting portion) and inside a sealing material 44 (on the side where a liquid crystal is present) in a finished liquid crystal display element.
Furthermore, since the display electrodes 46 of the display portion are wired in parallel at equal intervals, the wiring density of the display electrodes 46 is uniform, whereas the oblique straight wiring conductors 45 which are radially wired as described above is not uniform in wiring density. In particular, a liquid crystal display device such as an STN-LCD (super twisted nematic LCD) which needs a high-precision gap (.+-.0.1 .mu.m) between both electrode substrates is greatly affected by the effective density at which a spacer for creating the gap functions.
Accordingly, since the conventional radial oblique straight wiring conductors 41 is generally lower in wiring density than the display portion, uneven color occurs due to the variation in the gap in the frame portion. As described previously, the transparent electrodes are generally made of ITO film as thick as 0.2-0.3 .mu.m, and the spacer is supported by the display electrodes 46 and the oblique straight wiring conductors 45 which is made of ITO film on each of the upper and lower electrode substrates. This leads to the problem that the spacer becomes free in a portion in which no electrodes are present and gap control becomes ineffective.
Such an art is described in documents such as Japanese Patent Laid-Open Nos. 289626/1991, 70627/1992, 170522/1992, 369622/1992 and 127181/1993.
Although not known, the invention made by Fujii et al has been filed as a prior application (Japanese Patent Laid-Open Nos. 214785/1994) by the same applicant with respect to a liquid crystal display device having lead-out wiring conductors whose area use efficiency is high and each conductor of which has a short length and a low resistance.
Therefore, a first object of the present invention is to provide a liquid crystal display device suited to a narrow frame, which has an uniform black non-lighting area free of nonuniform shading in a frame portion, by optimizing the area occupation ratio of each ITO below a seal portion between a central portion and an end portion of each ITO.
A second object of the present invention is to provide a liquid crystal display device suited to a narrow frame, by generally taking account of the uniformalization of the gap near a frame portion and the uniformalization of the resistance of each ITO.